BATCH file to convert all WAV files into 32kbps bitrate mp3 files. You need to install ffmpeg first. I use this file to convert all Google NotebookLM WAV files that soo huge, and I'm afraid my students will object with them, if I share the raw.

wav_to_mp3_32kbps.cmd

@echo off
REM wav_to_mp3_32kbps.cmd
REM Batch script to convert .wav files to .mp3 at 32kbps.
REM It skips conversion if a .32k.mp3 version of the file already exists.

SETLOCAL EnableDelayedExpansion

echo Starting WAV to MP3 conversion (32kbps)...
echo ============================================

REM Ensure ffmpeg is in your PATH or place ffmpeg.exe in the same directory as this script.

FOR %%f IN (*.wav) DO (
    REM Get the filename without the .wav extension
    SET "basename=%%~nf"

    REM Define the target MP3 filename
    SET "outputfile=!basename!.32k.mp3"

    REM Check if the output file already exists
    IF EXIST "!outputfile!" (
        echo Skipping: "!outputfile!" already exists for "%%f".
    ) ELSE (
        echo Converting "%%f" to "!outputfile!"...
        ffmpeg -i "%%f" -b:a 32k -ar 44100 -ac 2 "!outputfile!"
        
        REM Check if ffmpeg conversion was successful
        IF ERRORLEVEL 1 (
            echo   [ERROR] Failed to convert "%%f". Check ffmpeg output.
            REM Optionally, delete a partially created/failed output file
            REM IF EXIST "!outputfile!" DEL "!outputfile!"
        ) ELSE (
            echo   [SUCCESS] Converted "%%f" to "!outputfile!".
        )
    )
    echo. REM Adds a blank line for better readability
)

echo ============================================
echo Conversion process finished.
ENDLOCAL
pause

if you can read the batch file, the script is actually check if there is a file named like filename.32k.mp3 exist. if exist, skip this conversion. If no, convert this wav into filename.32k.mp3. This script will do it for every wav files within current directory /folder

The magic is at line #25, the conversion with ffmpeg.

So... make sure you've ffmpeg in your path fists.

now live at

https://kampar.wordpress.com/2025/06/02/batch-file-to-convert-all-wav-files-into-32kbps-bitrate-mp3-files/